graft guile onto the layout logic

Makefile

@@ -6,8 +6,7 @@ DATADIR=$(PREFIX)/share
 MANDIR=$(DATADIR)/man
 
 CFLAGS=-g -Wall -Werror -Wextra -Wpedantic -Wno-unused-parameter $\
-	-Wno-overlength-strings -Wconversion -Wformat-security -Wformat $\
+	-Wno-overlength-strings -Wformat-security -Wformat -Wunused-result $\
-	-Wsign-conversion -Wfloat-conversion -Wunused-result $\
 	$(shell pkg-config --cflags wayland-client) $\
 	$(shell guile-config compile)
 LIBS=-lrt $\
@@ -45,3 +44,4 @@ clean:
 	$(RM) $(IMG)
 
 .PHONY: clean install uninstall all
+

riverguile.c

@@ -9,6 +9,7 @@
 #include <assert.h>
 #include <setjmp.h>
 #include <wayland-client.h>
+#include <libguile.h>
 
 #ifdef __linux__
 #include <features.h>
@@ -42,18 +43,88 @@ struct Output
 	bool configured;
 };
 
+struct Layout_demand_parameters
+{
+	uint32_t view_count, width, height, serial;
+	struct Output *output;
+};
+
+static bool scm2uint(uint32_t *x, SCM s)
+{
+	if ( scm_is_false(scm_number_p(s)) == 1 )
+		return false;
+	*x = scm_to_uint32(scm_inexact_to_exact(s));
+	return true;
+}
+
+static void *call_layout_demand_handler (void *data)
+{
+	struct Layout_demand_parameters *params = (struct Layout_demand_parameters *)data;
+
+	SCM call_result = scm_call(
+		scm_variable_ref(scm_c_lookup("layout-demand-handler")),
+		scm_from_uint32(params->view_count),
+		scm_from_uint32(params->width),
+		scm_from_uint32(params->height),
+		SCM_UNDEFINED
+	);
+
+	if ( scm_is_false(scm_list_p(call_result)) == 1 )
+		return (void *)"ERROR: layout-demand-handler did not return a list.\n";
+	if ( params->view_count != scm_to_uint32(scm_length(call_result)) )
+		return (void *)"ERROR: Length of list returned by layout-demand-handler does not match view count.\n";
+
+	for (uint32_t i = 0; i < params->view_count; i++)
+	{
+		SCM elem = scm_list_ref(call_result, scm_from_uint32(i));
+
+		if ( scm_is_false(scm_list_p(elem)) == 1 )
+			return (void *)"ERROR: View dimensions list is not a list.\n";
+		if ( scm_to_uint32(scm_length(elem)) != 4 )
+			return (void *)"ERROR: View dimensions list length does not equal four (x, y, width, height).\n";
+
+		uint32_t x, y, w, h;
+		if ( !scm2uint(&x, scm_list_ref(elem, scm_from_int(0)))
+			|| !scm2uint(&y, scm_list_ref(elem, scm_from_int(1)))
+			|| !scm2uint(&w, scm_list_ref(elem, scm_from_int(2)))
+			|| !scm2uint(&h, scm_list_ref(elem, scm_from_int(3))) )
+			return "ERROR: Encountered non-numerical view dimensions.\n";
+
+		river_layout_v3_push_view_dimensions(
+			params->output->layout,
+			x, y, w, h,
+			params->serial
+		);
+	}
+
+	return NULL;
+}
+
 static void layout_handle_layout_demand (void *data, struct river_layout_v3 *river_layout_v3,
 		uint32_t view_count, uint32_t width, uint32_t height, uint32_t tags, uint32_t serial)
 {
 	struct Output *output = (struct Output *)data;
-	for (size_t i = 0; i < view_count; i++)
+
+	struct Layout_demand_parameters params = {
+		.view_count = view_count,
+		.width = width,
+		.height = height,
+		.serial = serial,
+		.output = output,
+	};
+
+	void *res = scm_with_guile(call_layout_demand_handler, (void *)&params);
+
+	if ( res != NULL )
 	{
-		river_layout_v3_push_view_dimensions(
+		fputs(res, stderr);
-			output->layout, 0, 0,
+		loop = false;
-			width, height, serial
+		ret = EXIT_FAILURE;
-		);
+		return;
 	}
-	river_layout_v3_commit(output->layout, "()", serial);
+
+	// TODO if 'layout-name' variable exists, use it.
+	river_layout_v3_commit(output->layout, "(🐦)", serial);
 }
 
 static void layout_handle_namespace_in_use (void *data, struct river_layout_v3 *river_layout_v3)
@@ -63,10 +134,16 @@ static void layout_handle_namespace_in_use (void *data, struct river_layout_v3 *
 	loop = false;
 }
 
+static void *exec_user_command (void *str)
+{
+	return (void *)scm_c_eval_string((char *)str);
+}
+
 static void layout_handle_user_command (void *data,
 		struct river_layout_v3 *river_layout_manager_v3,
 		const char *command)
 {
+	(void)scm_with_guile(exec_user_command, (void *)command);
 }
 
 static const struct river_layout_v3_listener layout_listener = {
@@ -231,6 +308,106 @@ static void handle_error (int signum)
 	kill(getpid(), signum);
 }
 
+static void *load_script (void *data)
+{
+	/* Note: All guile objects are garbage collected. */
+
+	char *path = (char *)data;
+	(void)scm_c_primitive_load(path);
+
+	/* Check if the handler has been defined. */
+	SCM variable = scm_module_variable(
+		scm_current_module(),
+		scm_string_to_symbol(
+			scm_from_utf8_string("layout-demand-handler")
+		)
+	);
+
+	if ( scm_is_false(variable) == 1 )
+	{
+		ret = EXIT_FAILURE;
+		loop = false;
+		return (void *)"ERROR: Script does not define layout-demand-handler.\n";
+	}
+
+	return NULL;
+}
+
+static char *formatted_buffer (const char *fmt, ...)
+{
+	/* Determine length of formatted text. */
+	va_list args;
+	va_start(args, fmt);
+	/* +1 for NULL. */
+	unsigned long len = (unsigned long)vsnprintf(NULL, 0, fmt, args) + 1;
+	va_end(args);
+
+	char *buffer = calloc(1, len);
+	if ( buffer == NULL )
+	{
+		fprintf(stderr, "ERROR: calloc: %s\n", strerror(errno));
+		return NULL;
+	}
+
+	/* Finally write formatted text into buffer. */
+	va_start(args, fmt);
+	vsnprintf(buffer, len, fmt, args);
+	va_end(args);
+
+	return buffer;
+}
+
+static char *get_script_path (void)
+{
+	struct {
+		const char *fmt;
+		bool needs_env;
+		const char *env;
+	} paths[] = {
+		{ .fmt = "layout.scm",                       .needs_env = false, .env = NULL                      },
+		{ .fmt = "%s/riverguile/layout.scm",         .needs_env = true,  .env = getenv("XDG_CONFIG_HOME") },
+		{ .fmt = "%s/river/layout.scm",              .needs_env = true,  .env = getenv("XDG_CONFIG_HOME") },
+		{ .fmt = "%s/.config/riverguile/layout.scm", .needs_env = true,  .env = getenv("HOME")            },
+		{ .fmt = "%s/.config/river/layout.scm",      .needs_env = true,  .env = getenv("HOME")            },
+		{ .fmt = "/etc/riverguile/layout.scm",       .needs_env = false, .env = NULL                      }
+	};
+
+	char *path = NULL;
+	for (size_t i = 0; i < (sizeof(paths) / sizeof(paths[0])); i++)
+	{
+		if ( path != NULL )
+			free(path);
+
+		/* Path needs env var, but it is not set. */
+		if ( paths[i].needs_env && paths[i].env == NULL )
+			continue;
+
+		path = formatted_buffer(paths[i].fmt, paths[i].env);
+		if ( path == NULL )
+			return NULL;
+
+		/* Does the path exist? */
+		if ( access(path, F_OK) != 0 )
+			continue;
+
+		/* Is it readable? */
+		if ( access(path, R_OK) != 0 )
+		{
+			fprintf(stderr, "ERROR: Script '%s' exists, but is not readable.\n", path);
+			free(path);
+			return NULL;
+		}
+
+		return path;
+	}
+
+	if ( path != NULL )
+		free(path);
+
+	fputs("ERROR: No layout script found.\n", stderr);
+	return NULL;
+}
+
 int main(int argc, char *argv[])
 {
 	signal(SIGSEGV, handle_error);
@@ -238,6 +415,21 @@ int main(int argc, char *argv[])
 	signal(SIGINT, handle_interrupt);
 	wl_list_init(&outputs);
 
+	char *path = get_script_path();
+	if ( path == NULL )
+	{
+		ret = EXIT_FAILURE;
+		goto early_exit;
+	}
+
+	void *res = scm_with_guile(load_script, (void *)path);
+	if ( res != NULL )
+	{
+		fputs((char *)res, stderr);
+		ret = EXIT_FAILURE;
+		goto early_exit;
+	}
+
 	/* We query the display name here instead of letting wl_display_connect()
 	 * figure it out itself, because libwayland (for legacy reasons) falls
 	 * back to using "wayland-0" when $WAYLAND_DISPLAY is not set, which is
@@ -248,7 +440,7 @@ int main(int argc, char *argv[])
 	{
 		fputs("ERROR: WAYLAND_DISPLAY is not set.\n", stderr);
 		ret = EXIT_FAILURE;
-		goto cleanup;
+		goto early_exit;
 	}
 
 	wl_display = wl_display_connect(display_name);
@@ -256,7 +448,7 @@ int main(int argc, char *argv[])
 	{
 		fputs("ERROR: Can not connect to wayland display.\n", stderr);
 		ret = EXIT_FAILURE;
-		goto cleanup;
+		goto early_exit;
 	}
 
 	wl_registry = wl_display_get_registry(wl_display);
@@ -269,7 +461,6 @@ int main(int argc, char *argv[])
 		while ( loop && wl_display_dispatch(wl_display) > 0 );
 
 	struct Output *output, *tmp;
-cleanup:
 	wl_list_for_each_safe(output, tmp, &outputs, link)
 	{
 		wl_list_remove(&output->link);
@@ -282,5 +473,10 @@ cleanup:
 		wl_registry_destroy(wl_registry);
 	wl_display_disconnect(wl_display);
 
+early_exit:
+	if ( path != NULL )
+		free(path);
+
 	return ret;
 }
+